Here’s a quick way to create a sitemap in movable type (should work for 3.x, I’ve got it here on 4).
Create a new index template, save it as sitemap.xml (other names can work fine too if you want), then paste in the following:
<?xml version="1.0" encoding="UTF-8"?>
<lastmod><$MTEntryModifiedDate utc="1" format="%Y-%m-%dT%H:%M:%SZ"$></lastmod>
If you have any other specific pages you want to add, you can just put in an explicit <url> record, with a priority from 0 to 1.0, one receiving the most attention. You can also add a changefreq [daily|weekly|monthly] to help crawlers know when to look.
When you have that in place, go to the google webmaster tools to submit your sitemap, and add your rss feed while you’re at it.